1. Field of the Invention
The invention relates to amusement and exercise devices. Specifically, the invention is an apparatus for weight lifting exercise in which the weight is automatically increased or reduced during the repetitions of an exercise.
2. Description of the Prior Art
Body building requires that man exercise his muscles against an opposing force. One of the most common ways to accomplish the required exercise is to lift a heavy weight such as a barbell or the like. This form of exercise may be referred to as isotonic exercise, as the muscle acts against a constant weight. Ordinarily, the muscle is repeatedly exerted against the weight, accomplishing the identical movement with each repetition.
Well known isotonic exercise devices employ weight units of cast iron or other solid, dense material or employ resistance via pnumatic cylinders. Different numbers of the weight units may be selectively engaged by the user, for example by stringing the units on a barbell or lifting cable, and the user then performs as many exercise repetitions as he is able with the preselected weight.
It is known that the muscles tire with each repetition of an exercise, requiring that the weight selected for a movement be less than the maximum capacity of the muscles involved so that many repetitions can be accomplished, with the muscles eventually tiring to the point that they can no longer repeat the movement at the preselected weight. This method of body building is inefficient, as it requires that the muscles work at far less than full efficiency during the early repetitions of the movement, during which time the muscles are merely tiring themselves to the point where truly efficient body building can begin.
Serious body builders have attempted to eliminate the initial period of inefficient exercise by placing as much weight on, for example, a barbell as the muscle can lift in a single movement. Then, after each repetition or short series of repetitions, assistants at each end of the barbell will quickly remove one of the weight units, thereby reducing the total weight as the muscles tire, allowing the body builder to continue the same movement with efficiency. The inconvenience of this system is evident, but it also is dangerous, as the assistants must closely coordinate their efforts in order to avoid an unbalanced barbell in the hands of the body builder.
Isometric exercise employs the muscles against an unmoving object, allowing the muscles to apply full force for as long as the body builder desires. Although the muscles may tire, the exercise is uninterrupted, as no movement is involved. Isometric exercising devices are known that mechanically increase the force being opposed by the muscles, thereby forcing the muscles to exert their maximum effort. At some point, the force exerted by the device may overcome the muscle. Serious injury has resulted to persons using such isometric devices. U.S. Pat. Nos. 3,731,922 and 3,614,097 to Jungreis relate to variable force isometric devices. Such devices are not generally suited for isotonic exercise.
The present invention relates to an isotonic exercise apparatus that safely varies the mass of a dead weight to compensate fo muscle warm-up and fatigue.